High-voltage electric motors are becoming increasingly popular in industrial applications due to their higher efficiency and lower maintenance requirements than their mechanical counterparts. Traditionally, high-voltage motors contain large charge-storing devices that stabilize energizing power to the motor. During normal operation these charge storing devices may be capable of storing several thousand volts of potential energy. Even when the motor is powered down, the charge-storing devices may store high-voltage charges for substantial amounts of time. These charge-storing devices could, if not allowed adequate time to discharge, present a safety hazard to maintenance personnel and/or equipment operators that come in close contact with the motor. Thus, it may be desirable to detect a high-voltage condition associated with an electric motor and provide a warning signal indicative of the high-voltage condition.
One system for detecting the voltage level of a power source is described in U.S. Pat. No. 6,885,215 to Hou et al. (“the '215 patent”). The '215 patent describes a voltage detector circuit with a programmable threshold point. The detector includes a voltage following circuit connected to a power source for tracking the voltage value of the power source and a selectable threshold point circuit connected to the voltage following circuit to provide the threshold value. The voltage detector described in the '215 patent is configured to generate an output indicative of whether the value of the power source has increased above or decreased below the threshold value. In one instance, the threshold point is established by the amount of current provided by the threshold point circuit, which may further be determined by the size and type of transistor used in the selectable threshold point circuit.
Although the voltage detection circuit described in the '215 patent may be effective for detecting voltage levels corresponding to certain programmable threshold values, it may include several disadvantages. For example, the system described in the '215 patent may provide insufficient isolation between the detection circuitry and the processor circuitry. As a result, transient signals, such as voltage or current spikes, may damage the processor circuitry and/or other systems that are in contact with detection circuitry.
In addition, the voltage detection circuit described in the '215 patent may lack reliability. For example, because the detection circuit of the '215 patent operates exclusively from a primary power source, it may be incapable of operation in the event of a power failure. As a result, equipment systems that rely on continuous voltage detection even in the event of loss of power may become inoperable.
The disclosed high-voltage detection system is directed towards overcoming one or more of the problems set forth above.